Two amino acids can bond covalently forming a substituted amide bond, called a peptide bond:
To achieve this, the alpha carboxyl group of an amino acid has reacted with the alpha amino group of the other amino acid, and a water molecule has been lost:
Let's see it using the molecular models . Between the two amino acids, glycine and serine, the glycyl-serine dipeptide is formed:
The covalently bonds carbonyl carbon of the first amino acid with the amino nitrogen of the second one.
In the R groups have been removed, as well as all the hydrogen atoms except that bound to the nitrogen in the peptide bond. What is left of the dipeptide are the “backbone” atoms.
the geometry of the peptide bond. Atoms in the peptide bond and those directly bound to them (alpha carbon and oxygen in glycine, as well as alpha carbon and hydrogen in serine) are arranged on a plane .